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https://issues.apache.org/jira/browse/HADOOP-1463?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12513314
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Hairong Kuang commented on HADOOP-1463:
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> Can I ask for
> o Capacity (df total)
> o DFS Used
> o DFS Remaining ?
Koji's ask makes sense. I thought about the same too. But this feature requires
heartbeat proctocol change. Currently each heartbeat sends capacity and
remaining space and the namenode interprerates dfs used as a substraction of
capacity and remaing. For this ask, we can either
1. each datanode sends disk capacity at the registration time and then each
heartbeat sends dfs used space and remaining space; or
2. each datanode's heartbeat sends disk capacity (although it does not change
most of the time), dfs used space, and dfs remaining space.
> dfs should report total size of all the space that dfs is using
> ---------------------------------------------------------------
>
> Key: HADOOP-1463
> URL: https://issues.apache.org/jira/browse/HADOOP-1463
> Project: Hadoop
> Issue Type: Improvement
> Components: dfs
> Affects Versions: 0.12.3
> Reporter: Hairong Kuang
> Assignee: Hairong Kuang
> Fix For: 0.14.0
>
> Attachments: usedSpace.patch
>
>
> Currently namenode reports two statistics back to the client:
> 1. The total capacity of dfs. This is a sum of all datanode's capacities,
> each of which is calculated by datanode summing all data directories disk
> space.
> 2. The total remaining space of dfs. This is a sum of all datanodes's
> remaining space. Each datanode's remaining space is calculated by using the
> following formula: remaining space = unused space -
> capacity*unusableDiskPercentage - reserved space. So the remaining space
> shows how much space that the dfs can still use, but it does not show the
> size of unused space.
> Each dfs client caculates the total dfs used space by substracting remaining
> space from the total capacity. So the used space does not accurately shows
> the space that dfs is using. However it is a very important number that dfs
> should provide.
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